This application claims the benefit of the earlier filing date of Korean Patent Application No. 00-62025, filed Oct. 20, 2000, which is hereby incorporated by reference in its entirety.
The invention relates generally to a method of manufacturing a capacitor in semiconductor devices. More particularly, the invention relates to a method of manufacturing semiconductor devices that prevents defective Ru/BST/Ru capacitors by depositing a Ru lower electrode by means of a chemical vapor deposition (CVD) method, and then stabilizing the surface of the Ru lower electrode by a given thermal process. The invention can be used in a process of manufacturing a capacitor in a DRAM device having the integration degree of over 1 Gbit.
The current trend includes increasingly utilizing Ta2O5 or BST as a dielectric thin film for use in a SiO2/Si3N4/SiO2 stack structure in a DRAM. It is believed that in the near future, as a design rule, BST will be the most promising dielectric thin film in a DRAM over 1 Gbit. In a high quality actual device, the BST dielectric thin film can be formed on a patterned substrate by means of a chemical vapor deposition method. When BST is used as a dielectric thin film, its applications typically include a concave type Ru/BST/Ru capacitor or a stack type Pt/BST/Pt capacitor. When Pt is used as an electrode material, its capacitor characteristics are very stable due to its stable interface characteristic with BST, without regard to the its formation method or a post-process. On the other hand, when Ru is used as an electrode material, its capacitor characteristics become unstable because it degrades the quality of BST when BST is deposited. This is believed to be due to the easily oxidized characteristic of Ru and because of its low catalyst characteristic as compared to Pt. Thus, Pt allows very good BST film quality when BST is deposited by means of a chemical vapor deposition method because Pt contains a significant number of activated oxygen atoms due to its catalytic characteristic. However, Ru degrades the BST film quality because Ru tends to form a RuO2 oxidization phase, instead of activated oxygen atoms, without silver catalyst characteristic.
Furthermore, Ru must be processed at a very low temperature (250xcx9c270xc2x0 C.) in order to deposit Ru by means of the chemical vapor deposition method to prevent creation of RuO2. Due to these characteristics, Ru affects a BST thin film or an underlying anti-diffusion film because it contains a significant amount of carbon and oxygen during a subsequent process. Even with a flat structural layout, it is difficult to obtain good BST deposition characteristics on Ru by means of the chemical vapor deposition method. These hindrances have obstructed and delayed development of a concave type Ru/BST/Ru capacitor. It is believed that attempts have been made to perform a rapid thermal process (RTP) under nitrogen or argon atmosphere in order to obtain a good characteristic Ru film. Therefore, there is a need for a process to change the surface characteristics of Ru in order to improve an interface characteristic of BST/Ru for flat or curved surfaces.
It is therefore an object of the present invention to provide a manufacturing method that prevents defective Ru/BST/Ru capacitors in semiconductor devices by depositing a Ru lower electrode by means of the chemical vapor deposition method and then stabilizing the surface of the Ru lower electrode by a given thermal process.
According to the present invention, a BST/Ru interface that is characterized by low leakage current and dielectric constant can be obtained to improve the reliability of a capacitor.
In order to accomplish the above objects, a method of manufacturing a capacitor in semiconductor devices according to the present invention is characterized in that it comprises forming a silicon oxide film on a surface of a silicon substrate; forming a nitride film on said silicon oxide film; forming a contact hole by sequentially etching a portion of said nitride film and said silicon oxide film; depositing a doped polysilicon layer over the entire surface of said silicon substrate, said doped polysilicon layer filling said contact hole; performing an etch-back process to remove a portion of said doped polysilicon layer, said etch-back process leaving said doped polysilicon layer in said contact hole; forming an ohmic contact layer over said doped polysilicon layer in said contact hole; forming an anti-diffusion film on said ohmic contact layer; forming a silicate glass film over the entire surface of said silicon substrate including said anti-diffusion film; forming a concave hole by etching a portion of said silicate glass film, said concave hole having an internal wall; forming a Ruthenium lower electrode on said internal wall of said concave hole; forming a BST dielectric film on said first Ruthenium electrode, said forming said BST dielectric sequentially including performing a NH3-plasma process, performing a N2O-plasma process, and depositing BST; crystallizing said BST dielectric film, said crystallizing including performing a rapid thermal process; forming an upper electrode on said BST dielectric film, said BST dielectric film and said first and second Ruthenium electrodes forming a capacitor; and performing a thermal treatment to stabilize said capacitor.